Comprehensive Cytology: Cell Structure, Differentiation, and Cell Cycle

What is a cell?

The basic structural and functional unit of any living thing.

What does the cell theory state?

1. All living things are made of one or more cells. 2. All cells come from existing cells. 3. Cells are the basic building blocks of life.

What are the two main types of cells?

Eukaryotic cells and prokaryotic cells.

What are the characteristics of eukaryotic cells?

They can be unicellular or multicellular, have a nucleus, and contain organelles.

What are the characteristics of prokaryotic cells?

They are unicellular, never form tissues, lack a nucleus, and have no organelles.

What is cell differentiation?

The process by which cells become specialized in structure and function.

What are the outcomes of cell differentiation?

1. Different appearance and structure. 2. Functional specialization.

What is the function of the nucleus?

It serves as the information processing and administrative center of a eukaryotic cell.

What are the main components of the nucleus?

1. Nuclear envelope 2. Nucleoplasm 3. Chromatin and chromosomes 4. Nucleolus.

What is the nuclear envelope?

A selectively permeable barrier formed by two membranes that separates nucleoplasm from cytoplasm.

What is the role of nuclear pores?

They allow selective passage of large molecules between the nucleoplasm and cytoplasm.

What is chromatin?

A complex of DNA and proteins (histones) that condenses to form chromosomes.

Differentiate between euchromatin and heterochromatin.

Euchromatin is transcriptionally active, while heterochromatin is transcriptionally inactive or less active.

What is the nucleolus?

A dense cluster of RNA molecules and proteins involved in ribosomal RNA synthesis.

What is the significance of histones in chromatin?

Histones help package DNA into nucleosomes, which are essential for DNA replication and transcription.

What is the cell cycle?

The series of events that take place in a cell leading to its division and replication.

What are the two types of cell division?

Mitosis and meiosis.

What is the function of the nucleoplasm?

It serves as a suspension medium for other nuclear components.

What is a totipotent stem cell?

A stem cell that can differentiate into any cell type, including all embryonic and extra-embryonic cell types.

What are blastomeres?

The early cells formed by the division of a fertilized egg.

What is the role of the nuclear lamina?

It stabilizes the nuclear envelope and is associated with the inner membrane.

What is the structure of nucleosomes?

A core of eight histones wrapped by 150 base pairs of DNA.

What is the diameter of DNA in its double helix form?

2 nm thick.

What is the significance of the 30 nm thick fibers of packed nucleosomes?

They represent a higher level of DNA packaging during interphase.

What is the primary function of ribosomal RNA produced in the nucleolus?

To form the structural and functional components of ribosomes.

What is the difference between diploid and haploid cells?

Diploid cells contain two sets of chromosomes, while haploid cells contain one set.

What is the total number of chromosomes in human cells?

46 chromosomes (23 pairs).

What is the structure of chromatin in active cells?

Larger loops of coiled DNA (300 nm thick) with slightly basophilic areas.

What type of microscopy is used to observe chromatin?

Transmission Electron Microscopy (TEM).

What is the difference between euchromatin and heterochromatin?

Euchromatin is loosely packed and transcriptionally active, while heterochromatin is tightly packed and transcriptionally inactive.

What are chromosomes visible during?

Mitosis and meiosis.

What is the ploidy of somatic cells?

Diploid (2n) with 22 pairs of autosomes and 1 pair of sex chromosomes.

What is the ploidy of gametes?

Haploid (n) with 22 autosomes and either one 'X' or 'Y' sex chromosome.

What is the function of the nucleolus?

Ribosome production through dense concentration of rRNA.

What are the four phases of the cell cycle?

G1, S, G2, and Mitosis.

What occurs during the S phase of the cell cycle?

DNA replication and histone synthesis.

What is the quiescent state of a cell called?

G0 phase.

What happens during prophase of mitosis?

Nucleolus disappears, chromatin condenses, and the mitotic spindle forms.

What occurs during metaphase of mitosis?

Chromosomes align at the equator of the cell.

What is the outcome of anaphase in mitosis?

Sister chromatids separate and migrate to opposite poles.

What occurs during telophase of mitosis?

Chromosomes decondense, and the nuclear envelope reassembles.

What is cytokinesis?

The process that divides the cytoplasm, resulting in two daughter cells.

What is the role of stem cells?

To renew differentiated cells and maintain tissue homeostasis.

What is the difference between stem cells and progenitor cells?

Stem cells are undifferentiated and can divide asymmetrically, while progenitor cells are committed to differentiation.

What is the significance of meiosis?

It produces four unique haploid cells from one diploid cell, increasing genetic variability.

What occurs during prophase I of meiosis?

Crossover between homologous chromosomes occurs, forming tetrads.

What is the result of meiosis II?

Four haploid daughter cells with haploid chromosomes.

What is a karyotype?

A display of the complete set of chromosomes in an organism.

What are the three types of materials in the nucleolus?

Fibrillar Centers (FC), Fibrillar Material (F), and Granular Material (G).

What is the function of the cytoskeleton?

To provide structural support and facilitate cell movement.

What is the role of inclusions in a cell?

To store substances and assist in cellular functions.

What is the significance of the G1 phase?

It is usually the longest phase where the cell grows and prepares for DNA synthesis.

What happens during the late telophase?

Chromosomes return to an uncondensed state and cytokinesis begins.

What are the two main categories of organelles?

Membranous and non-membranous organelles.

Name three non-membranous organelles.

Microtubules, ribosomes, and proteasomes.

What is the primary function of ribosomes?

Protein synthesis.

What distinguishes rough endoplasmic reticulum (RER) from smooth endoplasmic reticulum (SER)?

RER has ribosomes on its surface, while SER does not.

What is the function of the Golgi apparatus?

Post-translational modification, packaging, and distribution of proteins.

What are lysosomes responsible for?

Cellular digestion and autophagy.

What is the main role of mitochondria?

ATP synthesis and lipid metabolism.

What is the structure of mitochondria?

They have two membranes: an outer membrane and a highly folded inner membrane.

What is the function of peroxisomes?

Detoxification and lipid metabolism.

What is the cytoskeleton composed of?

Microtubules, microfilaments, and intermediate filaments.

What is the role of microtubules in the cell?

They provide structural support and facilitate movement of organelles.

What are the two subunits of ribosomes?

Small subunit (40S) and large subunit (60S).

What is the function of the rough endoplasmic reticulum?

Synthesis of proteins and glycosylation.

What is the significance of the Golgi apparatus's cis face?

It is the receiving region for proteins from the RER.

What are the characteristics of smooth endoplasmic reticulum?

It has tubular membranes and is involved in lipid synthesis and detoxification.

How do mitochondria replicate?

They divide by binary fission.

What is the function of centrosomes?

They organize microtubules and are involved in cell division.

What is the process of 'treadmilling' in actin filaments?

It refers to the dynamic addition and loss of actin monomers at opposite ends of the filament.

What are heterolysosomes?

Active lysosomes involved in digestion.

What is the role of cytochrome C in mitochondria?

It activates proteases that lead to apoptosis.

What is the primary function of the endoplasmic reticulum?

Site of major metabolic activities, including lipid and protein synthesis.

What is the appearance of cells with well-developed rough ER under light microscopy?

They exhibit cytoplasmic basophilia.

What are the two regions of mitochondria?

The innermost matrix and the intermembrane space.

What is the role of the Golgi apparatus's trans face?

It is the shipping region where proteins are sorted and sent to their destinations.

What is the significance of the smooth ER in liver cells?

It is involved in detoxification of harmful substances.

What are microfilaments?

Stable polymers that provide mechanical stability to cell structures.

What is the role of keratin filaments in epithelial cells?

They form tonofibrils that attach to junctions, providing stability.

What is the function of the plasma membrane?

It acts as a selective barrier, regulating the passage of materials in and out of the cell.

What is the fluid mosaic model?

A model describing the plasma membrane as a mosaic of components with fluid characteristics.

What is the structure of the plasma membrane?

It consists of a lipid bilayer with embedded proteins, cholesterol, and oligosaccharide chains.

What are the main components of the plasma membrane?

Phospholipids, cholesterol, proteins, and oligosaccharides.

What is the function of integral proteins in the plasma membrane?

They span the membrane and are involved in transport, signaling, and structural functions.

What are peripheral proteins?

Proteins that do not span the membrane and are bound to only one membrane surface.

What is the glycocalyx?

A fuzzy external material formed by carbohydrate moieties of glycoproteins and glycolipids.

What is the role of cholesterol in the plasma membrane?

It provides rigidity and fluidity to the membrane.

What is simple diffusion?

A passive transport mechanism for fat-soluble and small non-charged molecules.

What is the difference between phagocytosis and pinocytosis?

Phagocytosis is cell eating (large particles), while pinocytosis is cell drinking (fluids).

What is receptor-mediated endocytosis?

A process where receptors on the membrane bind ligands, leading to vesicle formation.

What are lipid rafts?

Thicker regions of the membrane with high concentrations of cholesterol and glycosphingolipids.

What is the function of pumps in the plasma membrane?

They utilize ATP to move ions and solutes against their concentration gradients.

What are the functions of glycoproteins?

They play roles in cell recognition, adhesion, and response to hormones.

What is the significance of the asymmetry of cell membranes?

It allows for different functions and interactions on each side of the membrane.

What is the role of vimentin in cells?

It is an intermediate filament found in most cells derived from embryonic mesenchyme.

What are inclusions in cells?

Accumulations of metabolites and other substances with little or no metabolic activity.

What is the function of structural proteins in the plasma membrane?

They form junctional complexes with neighboring cells.

What are the main functions of the plasma membrane?

To act as a selective barrier, facilitate transport, and allow cell-environment interactions.

How do proteins in the plasma membrane move?

They can move laterally within the membrane, but their mobility can be restricted.